-LRB- CNN -RRB- -- The hostage crisis in eastern Algeria is over , but the questions remain .

Among them , exactly how many people are unaccounted for at a remote natural gas facility after three days of chaos that ended Saturday , leaving at least 23 hostages and dozens of Islamist militants dead .

Some 685 Algerian workers and 107 foreigners were freed , the Algerian Interior Ministry said .

Britain 's BP said Sunday four of its workers remain unaccounted for . And Norway 's Statoil said five of its employees were missing , while 12 others are now home in Norway , Algeria and Canada .

`` Search efforts are ongoing at the gas installation , looking for more possible victims . I fear the numbers will be updated with more victims later today when the search operation is expected to end , '' said Mohammed Said , Algeria 's communication minister .

The attackers came from six countries -- only three were Algerian -- and included Arabs and Africans , Said told state-run Radio Algeria . Algeria 's military found numerous `` foreign military uniforms '' in its sweep of the In Amenas facility , its Interior Ministry said .

Mauritania 's Sahara Media news agency said Sunday it had a video from Moktar Belmoktar , who leads the Al-Mulathameen Brigade associated with al Qaeda in the Islamic Maghreb that regional media have reported was behind the attack .

In it , Belmoktar said , `` We at al Qaeda are claiming responsibility of this blessed guerrilla operation . ''

Belmoktar has communicated with this and other news sites before , said Andrew Lebovich , a Senegal-based security analyst . But the news agency did not post the video , and CNN has not independently confirmed its authenticity .

Eleven former hostages -- among them British citizens -- have gotten medical treatment and psychological counseling from the U.S. military at a U.S. naval base in Sigonella , Italy , a U.S. official said Sunday . The hostages were brought from Algeria to the base Friday , the official said , and are being flown to their home countries as their conditions warrant . The remains of one American hostage were also brought to the base , the official said .

In a statement Saturday night , the White House said it was in close contact with Algeria 's government to `` gain a fuller understanding of what took place . ''

British Foreign Secretary William Hague echoed those remarks , adding his government is `` working hard to get definitive information '' about each individual .

Japan has 10 citizens -- likely affiliated with JGC Corp. , an engineering firm that was involved in gas production in In Amenas -- who are yet to be confirmed safe , in addition to a number of dead .

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Such Islamist militant activity is not new to Africa , including recent violence in Mali and Somalia .

Algeria 's status as Africa 's largest natural gas producer and a major supplier of the product to Europe heightens its importance to those who want to invest there . Yet that interest is coupled with pressure to make sure foreign nationals , and their business ventures , are safe .

Youcef Yousfi , Algeria 's energy and mining minister , insisted Sunday his country can keep its gas facilities secure and ruled out foreign forces coming in to help .

`` We are going to strengthen security , and we rely first on our means and resources , '' Yousfi said , according to the official Algerian Press Service .

Raids turn deadly

Militants in pickup trucks struck the sprawling gas complex about 50 kilometers -LRB- 30 miles -RRB- west of the Libyan border at dawn Wednesday , gathered the Westerners who worked there into a group and tied them up .

The In Amenas plant is run by Algeria 's state oil company , in cooperation with foreign firms such as Statoil and BP , and because of that employed workers from several countries .

The kidnappers wielded AK-47 rifles and put explosive-laden vests on some hostages , according to a U.S. State Department official .

Algeria said the attack was in retaliation for allowing France to use Algerian airspace for an offensive against Islamist militants in neighboring Mali .

And Sahara News ' report Sunday claimed Belmoktar said `` 40 immigrant Jihadists and supporters of Muslim countries '' led the siege in retaliation for the Mali offensive .

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But regional analysts believe it was too sophisticated to have been planned in just days .

On Thursday , Algerian special forces moved in because the government said the militants wanted to flee to Mali .

The Islamic extremists also planned to blow up the gas installation and rigged it with mines throughout , the U.S. official said .

Thursday 's military incursion succeeded in freeing some hostages -- but not all .

Some survivors described their harrowing escapes by rigging up disguises and sneaking to safety with locals , with at least one survivor running for his life with plastic explosives strapped around his neck .

Several hostages died . And the Algerian military came under criticism from some quarters for unnecessarily endangering hostages ' lives .

Undeterred , the government followed with a second push Saturday . That assault killed the remaining hostage-takers but resulted in more hostage deaths .

The army intervened `` to avoid a bloody turning point of events in this extremely dangerous situation , '' the Algerian Interior Ministry said Saturday .

`` It was clear that the terrorists were determined to escape the country with the captives and to bomb the gas installations . ''

On Sunday , an American lawmaker said the Algerian government turned down U.S. offers to help during the crisis .

`` They decided they were going to handle it their way , '' said Rep. Mike Rogers , a Michigan Republican who is chairman of the U.S. House Intelligence Committee . `` They did not want us or the other hostage nations involved in the decision-making . ''

British Defense Secretary Philip Hammond called the loss of life `` appalling and unacceptable , '' while laying blame solely on the terrorists .

Countries mourn dead , try to track down missing

While the military part of the operation is over , the searching and mourning is not for people in countries worldwide . In addition to combing the sprawling desert site , Algerian forces are searching hospitals and medical centers around the country , as well as towns and villages near the targeted site , according to a statement Sunday from Statoil .

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Colombia

Colombia 's president said a citizen was presumed dead .

France

No known French hostages are unaccounted for , France 's Defense Ministry said Saturday .

One man -- identified as Yann Desjeux -- died after telling the French newspaper Sud Ouest on Thursday that he and 34 other hostages of nine different nationalities were treated well . Three others who had been held are safe .

Japan

There are still 10 Japanese who have yet to be confirmed safe , JGC -- the engineering firm -- said Sunday .

Malaysia

Three hostages were on their way back to Malaysia , the country 's state-run news agency reported Sunday . But there is a `` worrying possibility '' that another is dead , while a fifth is unaccounted for , the agency said .

Norway

Five Norwegians are missing , while eight are safe , Norwegian Prime Minister Jens Stoltenberg said . `` We know that there are many fatalities , '' Statoil CEO Helge Lund said Sunday . `` A new day without answers has increased our concern . ''

Romania

One Romanian lost his life , the country 's Foreign Ministry said Saturday . Four other Romanians were freed .

United Kingdom

Three British citizens were killed , the Foreign Office said Sunday . Three other British nationals and a UK resident are also `` believed dead , '' he said . Twenty-two other Britons who were taken hostage have safely returned home .

United States

At least one American , identified as Frederick Buttaccio , is among the dead , the State Department said . Six freed Americans left Algeria and one remained .

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CNN 's Paul Cruickshank , Slma Shelbayah , Kevin Bohn , Barbara Starr and Per Nyberg contributed to this report .

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NEW : An Algerian official says Algeria does n't need help securing its energy facilities

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NEW : Algerians are searching hospitals , villages and more for missing , Statoil reports

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The number of those killed in the crisis will likely go up , an Algerian official says

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A new video reportedly claims responsibility in the name of al Qaeda